1. Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for transmitting a sounding reference signal in a wireless communication system.
2. Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) evolved from a universal mobile telecommunications system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) evolved from the 3GPP LTE.
An uplink reference signal may be classified into a demodulation reference signal (DMRS) and a sounding reference signal (SRS). The DMRS is a reference signal used in channel estimation for demodulation of a received signal. The SRS is a reference signal transmitted for uplink scheduling by a user equipment to a base station. The base station estimates an uplink channel by using the received SRS, and the estimated uplink channel is used in uplink scheduling.
Various uplink signals such as an uplink reference signal may be transmitted periodically. However, a periodic transmission of the uplink signal may cause a significant interference in a specific frequency region by forming a specific tone. In addition, a plurality of periodic signals may cause a narrowband interference formed with a plurality of tones.
It is necessary to mitigate an interference caused by a periodic uplink transmission.